What was the secret government program where federal agents infiltrated, spied on, and tried to discredit antiwar groups?

There were many attempts by the federal government to discredit the antiwar movement, and other movements during the 1960s. The FBI famously put civil rights workers, student group leaders, union officials, and others associated with the left under surveillance throughout the 1960s in a program known as COINTELPRO. Under this program, Martin Luther King, as well as almost every left-wing organizational leader were followed, wiretapped, and otherwise harassed in an attempt to disrupt and discredit...

There were many attempts by the federal government to discredit the antiwar movement, and other movements during the 1960s. The FBI famously put civil rights workers, student group leaders, union officials, and others associated with the left under surveillance throughout the 1960s in a program known as COINTELPRO. Under this program, Martin Luther King, as well as almost every left-wing organizational leader were followed, wiretapped, and otherwise harassed in an attempt to disrupt and discredit their actions. These attempts took place under the leadership of FBI director J. Edgar Hoover.

Another example was Operation CHAOS, a clandestine espionage program instituted by the CIA under Lyndon Johnson and extending into the 1970s. Operation CHAOS began as an attempt to connect antiwar groups to foreign, particularly Soviet influences, but, like the FBI's efforts, it spread to include civil rights organizations and others. Operation CHAOS was terminated amid the uproar over Watergate, and its activities were disclosed in the hearings that followed. Howard Zinn argues that these activities, along with many others, were widely ignored by the mainstream media:

It was typical of the selective coverage of important events by the television industry: bizarre shenanigans like the Watergate burglary were given full treatment, while instances of ongoing practice...were given the most fleeting attention. Dirty tricks against the Socialist Workers Party, the Black Panthers, other radical groups, had to be searched for in a few newspapers. The whole nation heard the details of the quick break-in at the Watergate apartment; there was never a similar television hearing on the long-term break-in at Vietnam.

The program was, however, fully exposed in the New York Times, in 1974, in an article that prompted a full congressional investigation into the domestic activities of the CIA. A similar investigation led to the following statement about the activities of COINTELPRO:

Many of the techniques used would be intolerable in a democratic society even if all of the targets had been involved in violent activity, but COINTELPRO went far beyond that...the Bureau conducted a sophisticated vigilante operation aimed squarely at preventing the exercise of First Amendment rights of speech and association...

The investigation further revealed that every president from Franklin Roosevelt to Richard Nixon had not only been aware of these activities, but actually received regular reports of their findings.

Source: Howard Zinn, A People's History of the United States (New York: Harper Perennial, 1995), 535.